Rear brake noise

[Maxmanta]

Hi, all......

Sorry for the tech-n00b question, but there's a whistling/squeaking noise coming from my rear brake when going slow, then a brief "groan" right before I stop.  The groan seems to sound at a specific point on the rotor.

I looked at the rear pads and there still seems to be plenty of meat on them.

What can be wrong here?  Is the runout on the rotor OHL?

[Cwaig]

Mine had that - I borrowed a runout gauge off a mate to check it, was a warped rear disc (as it had it before 1st service, got replaced under warranty).